1. Field of the Invention
The present invention relates generally to switching converters.
2. Description of the Related Art
Switched-mode voltage regulators provide superior voltage conversion efficiency because they regulate an output voltage with transistor switches that are either on or off so that they never operate in the linear region in which both current and voltage are nonzero. Because at least one of transistor current and voltage is therefore always close to zero, dissipation is greatly reduced.
These regulators often operate in two different operational modes. When current demand is high, they preferably operate in a pulse-width modulation mode and, when current demand is low, they are preferably switched to a pulse-frequency modulation operational mode. The latter mode enhances operational efficiency because it eliminates switching losses in the transistor switches. It has been found, however, that transitioning between these operational modes is slow, is sensitive to transient noise signals, and, often prone to circuit instabilities.